The phrase "designated number" refers to a specific or assigned number for a particular purpose or person. It can be a way to identify someone or something uniquely. Full definition
If you have to cancel, it must be within the plan's designated number of days prior to departure. (travelinsurancereview.net)
The dates she liked didn't write her back, and her own profile attracted crickets (and worse Number sequencing next to course name means the following: first digit designates the number of lecture hours for the course; the second digit designates (myintimcity.com)
Note: The supply of available 1 - 800 numbers has dwindled, so the phone companies are now designating numbers with prefixes of 888, 877, and 866 as toll - free numbers. (educationworld.com)